In manufacturing next generation three-dimensional memories and beyond, it is needed to etch a high aspect ratio shape. For example, in manufacturing an ReRAM, a stacked structure composed of a diode as a rectifier element, a variable resistive film, and a metal wire needs to be etched with a high aspect ratio. Moreover, with recent scaling of semiconductor devices, the aspect ratio of a processing shape tends to further increase.
For realizing processing of a high aspect ratio shape, a material having selectivity to a processing target film is preferably used as a hard mask for etching. However, the aspect ratio of a pattern of the hard mask itself becomes high for processing a high aspect ratio shape.
Conventionally, when processing a structure of an ReRAM, a stacked film of SiN and SiO2 is used as a hard mask. The aspect ratio of a processing shape tends to become high also in an ReRAM and therefore the aspect ratio of a hard mask also becomes high. For example, in the case of processing a narrow line shape with a line width of about 24 nm, if a stacked film of SiN and SiO2 is used as a hard mask, the aspect ratio of the hard mask becomes about 20. This is too large with respect to the aspect ratio of 10 that raises concerns about collapse. If the hard mask collapses during etching, desired processing cannot be performed.
Therefore, a manufacturing method of a semiconductor device capable of dealing with formation of a high aspect ratio shape is desired.